COMPARISON OF ACTIVATED SLUDGGE FLOCK STRUCTURE AND MICROBIAL FAUNA OF TWO HUNGARIAN WASTEWATER TREATMENT PLANTS

Activated sludge consists of bacteria, protozoa and metazoa species, but the major components of sludge flocks are active bacterial cells. The bacteria are responsible for the main biodegradation processes, such as carbon oxidation, nitrification, denitrification, phosphorous accumulation etc. The protozoa and metazoa community of the wastewater do not take part in the basic pollutant removal processes, but they live in close relationship with the bacteria and influence flock formation. Because of this interaction the protozoa species can be used as bioindicators of wastewater treatment plant performance. Activated sludge of two Hungarian waster treatment plant was examined, and the main flock properties and protozoa community of the sludge were determined. Although the capacity, the efficiency and the technology of the two wastewater treatment plants were very similar, the characteristic of the two activated sludge was found to be quite different. The diversity of the protozoa community and the number of found species were significantly dissimilar in the sludge samples of the two plants. No clear correlation could be made between the found indicative protozoa species and the treatment performance. The conclusion was that every wastewater treatment plant has a specific microorganism community, which is not directly determined by the characteristics of the wastewater or the treatment technology. Therefore long term microscopic tracking of activated sludge flock structure and microorganisms at a particular plant can provide more information about treatment performance, then the comparison of microbial fauna of different plants.